The present invention relates to a vehicle equipped with a hydraulically-operated device.
In view of the demand for the fuel economy, there has been proposed a hybrid vehicle in which an economy mode (Eco-mode) is selectable. The Eco-mode may be turned ON or activated by pressing an Eco-mode switch. When the Eco-mode is thus selected, the engine output torque is changed from the torque that is required during normal operation of the vehicle to the torque that is controlled for energy saving so that the engine of the vehicle is operated with efficiency. Such vehicle is disclosed, for example, by Japanese Unexamined Patent Application Publication No. 2008-105532.
In the hybrid vehicle disclosed in the above-cited Publication, the improvement of the fuel economy and the simultaneous maintenance of the required vehicle performance (the required torque) are accomplished by operating the engine efficiently and supplementing the engine with torque using a motor in the Eco-mode. Unlike such hybrid vehicle, however, in the vehicle that is powered by an engine and has no motor, no torque can be supplemented to the engine.
Therefore, in a forklift truck powered by an engine that is equipped with a hydraulically-operated device, there is a fear that an engine stall may occur in the Eco-mode due to insufficient engine torque attributable to a rapid increase of the load occurring during the loading operation. Particularly, immediately after a start of the engine, for example, the engine is not sufficiently warmed up and the engine output is yet to be stabilized. Furthermore, the hydraulic oil for hydraulically-operated device is low in temperature and high in viscosity. Such factors increase the load on the forklift truck and an engine stall may be caused easily.
The present invention, which has been made in view of such problems underlying the background art, is directed to providing a vehicle equipped with a hydraulically-operated device that prevents the occurrence of an engine stall successfully.